In a prior art coextrusion die of the above mentioned type each extrudable material is supplied in liquid state through a centrally located supply conduit which is connected to a system of radially extending distribution channels, each system being provided in a distribution plate, and is then passed into an annular collecting chamber from which it is passed into a common annular extrusion slot.
Due to the presence of the radially extending distribution channels in the prior art coextrusion there is insufficient space for the strong clamping bolts which are required to maintain the distribution plates sufficiently tensioned to avoid leakage of extrudable materials between said plates at high extrusion pressures.
The prior art supply system for extrudable materials comprising centrally located supply conduits also suffer from the drawback that it allows no space at the centre of the die for the provision of driving means when it is desired to rotate the inner and outer die parts relative to one another or for the provision of supply and discharge conduits for gaseous coolant, such as air to cool and expand the extruded tubular film. In the absence of such cooling, the production rate is considerably reduced.
The object of the invention is to provide a coextrusion die providing sufficient space for the provision of clamping bolts, means for rotating one of the die parts relative to one another and supply and discharge conduits for gaseous coolant.